The present invention relates to an arrangement to provide an accurate time-of-arrival indication for a plurality of received signals, such as the group of pulses in the synchronization preamble of a modern communication, navigation and/or identification system.
Modern communication, navigation and identification systems often require accurate time-of-arrival (TOA) measurements or indications of received signals. One possible receiver construction is based on the use of a matched filter whose impulse response is the time-reversed signal waveform with an appropriate delay. The matched filter acts as a signal correlator and serves to detect the received signal and to estimate the instant in time when the received signal appears to be best aligned with the stored finite-duration matched waveform.
Possible approaches of the implementation of the correlator may be utilizing a continuous-time device, such as surface acoustic wave (SAW) device or a discrete-time device, such as a charge-coupled device (CCD) and digital correlator (DC). The discrete-time implementation of the signal correlator is very attractive in certain application areas where module size, cost and construction flexibility and expandability are of concern. The associated sampling losses for a discrete-time system can be classified into two areas:
(1) Sampling Signal Loss--The received signal may not be sampled at the time instant that the signal-to-noise ratio (instantaneous) is locally maximum due to the timing uncertainty. PA1 (2) TOA Measurement Error--The accuracy of the TOA measurement is limited by the sampling rate (1/T) directly, i.e., the maximum TOA measurement error of .sup..+-. T/2 may occur under a single pulse operation, where T is the sampling clock time spacing.
These two associated losses may be reduced by increasing the sampling rate for better timing resolution at the cost of circuitry complexity.
In practice, a system usually provides a group of pulses in the synchronization preamble made to enhance system detection performance and anti-jamming capability.